A band of political radicals seized the reins of power in post-tsarist Russia a century ago this week, installing Vladimir Lenin as their first leader and setting in play some of the forces that made the 20th century the bloodiest in human history. It’s hard, in fact, to imagine just how different today’s world would be had Lenin and his comrades failed in their coup and had the Soviet Union never been established.

World War I likely would have ended about the same — Lenin withdrew Russia from the war only nine months before the general armistice — but the politics of Europe would have played out much differently, especially after the murderous Josef Stalin succeeded Lenin (who also had no qualms about using violence to cement power). But would any of the other forces vying for power after the fall of the tsar have ruled Russia less harshly or more democratically than the Bolsheviks, whose rise sparked a five-year civil war? Had democracy prevailed, would Russia have colluded with Adolf Hitler in invading Poland in 1939, sparking World War II? Would Soviet soldiers have been as effective in repelling a Nazi invasion of Russia without the iron fist of Stalin forcing them on?

The postwar shape of Europe, with communist satellites in the east facing off against the Western democracies, would not have been the same if the Soviet Union had not been vying with the rest of the Allied nations for territory at the dawn of the Cold War. But without Stalin, might fascism have taken a firmer, broader root across Eastern Europe, perhaps even in Russia itself, with its history of anti-Semitic pogroms?

These are subjects for idle speculation since, obviously, Stalin did succeed Lenin, and the Soviet Union persevered until 1991. Despite its inherent flaws as a political system, communism spread globally — with the help of Soviet agents in some places, through insurrections by emboldened Marxist true believers in others. Mongolia was first (aided by Russian troops) in 1921 but was followed over time by China, Vietnam, North Korea, Angola, Congo and Cuba, among others.

Throughout, communism enabled brutal totalitarians — Stalin’s reign of terror killed millions through forced collectivization of agriculture and ethnic cleansing programs, as well as the execution of perceived rivals, political heretics and resisters. The Cold War became a struggle by the Soviet Union to spread communism and by the West — led by the United States — to spread democratic capitalism around the world, each seeking dominance or at least hoping to block the advance of the other. In the process, smaller nations and insurrectionary forces became pawns in a series of proxy wars, as each of the two superpowers invested billions in their nuclear arsenals. But in the end, it was economic collapse (in part from the excessive defense spending) and emboldened citizenry that led to the Soviet Union’s demise in 1991.

The rise of international communism also, perversely, influenced domestic policy here in the U.S. When the Great Depression eroded faith in capitalism, President Franklin Delano Roosevelt turned to quasi-socialistic policies such as Social Security, public jobs programs (the Works Progress Administration and the Civilian Conservation Corps) and the Rural Electrification program that extended power to remote areas through local cooperatives using federal loans to hire the unemployed. If communism hadn’t been rivaling capitalism for political support, those New Deal programs might not have gained political traction.

How else do the Bolsheviks echo today? Through the communist regimes that remain (in various forms), from Cuba to Vietnam to China. And in Americans’ almost Pavlovian distrust of government-led communal action, left over from the Cold War. Never mind that such things as pooled-risk insurance, the national park system, interstate freeways and all manner of other government services we rely on are born of the recognition that shared risk and shared wealth can in many instances provide broad benefits for all without threatening individual liberty. But the Bolsheviks also echo through the anguished screams of the executed, the whimperings of the starving, the remembered betrayals of neighbors and relatives for the sake of the party. And they echo in the reminder that democracy lives and dies on the faith and willingness of the people to embrace and sustain it. As Hitler’s political rise in a democratic Germany taught us, even democracy is not safe from totalitarianism. So maybe the rise of the Bolsheviks echoes loudest in its warning of how precarious democracy can be.